Cooling methods and grate coolers of this type are well known in the art in various embodiments.
From tests and observations on known grate coolers, for example for cooling cement clinker, it is known that in the case of these coolers which are used in practice the effective useful volume for bulk material to be cooled (e.g. cement clinker) reduces in the transport direction along the surface of the cooler grate. This means that a relatively large cooler grate surface is required, particularly in the zones which are to the rear in the transport direction on the after-cooling zones, in order to cool the bulk material sufficiently. This situation is briefly explained with the aid of FIG. 6 of the drawings, which have been kept quite schematic.
In FIG. 6, a grate cooler which is shown quite schematically at 1 has an inlet shaft 2 for hot bulk material (e.g. cement clinker) coming from a kiln and a cooler grate surface 3 which extends in the longitudinal direction of the cooler between a cooler inlet 1a and a cooler outlet 1b. Thus this cooler grate surface 3 forms a transport surface for bulk material 4 to be cooled, and--as is known per se--it has essentially alternating rows (cross-rows) 3a and 3b respectively of grate plates 5 and 6 which are respectively fixed and movable to and fro, are provided with gas openings and through which cooling gas or cooling air (cf. broken arrows 7) flow upwards from the bottom in cross-current.
If one considers the representation in FIG. 6, then it will be recognised that--as shown by layers of bulk material 4a and 4b which are left blank or hatched respectively--there is a reduction in the effective cooling volume in the bulk material transport direction (arrow 8); this reduction can counteract the principle of the rising bed height in the transport direction, at least in the so-called recuperative zone, if the grate cooler is constructed in the form of a step grate cooler--as is also generally known. By means of a rise in the bulk material bed height the effective cooling volume can then be kept approximately constant, but the overall bed height in the transport direction and accordingly also the pressure loss for the cooling air rises.
The situation is similar with other known constructions, of which U.S. Pat. No. 4,624,636 may be mentioned as an example. According to FIG. 1 of that document, the gas openings of the grate plates which form the cooler grate surface can clearly be so large that a certain quantity of fines of the bulk material to be called falls downwards through them, where it is collected from specially constructed compartments and removed, that is to say a certain screening of the fine material travelling along directly on the cooler grate surface out of the lowest layer of material can fall out downwards along the entire surface of the cooler grate, and a suitably accurate control of this quantity of fines which falls out downwards encounters difficulties.
The object of the invention, therefore, is to improve a method and a grate cooler in such a way that by relatively simple and readily controllable means a particularly intensive cooling effect can be achieved with comparatively low investment and operating costs.
Advantageous embodiments of the invention are the subject matter of the subordinate claims.